The present invention relates to a technique for assembling motor stators. More particularly, the present invention relates to a method and apparatus for insertion of coil windings into a stator.
Electric motors of various types are commonly found in industrial, commercial and consumer settings. In industry, such motors are employed to drive various kinds of machinery, such as pumps, HVAC systems, conveyors, chillers, compressors, fans and so forth, to mention only a few. Conventional alternating current electric (ac) motors may be constructed for single or multiple phase power, and are typically designed to operate at predetermined synchronous speeds, such as 3600 rpm, 1800 rpm, 1200 rpm, and so on. Such motors generally include a stator, comprising a multiplicity of coils, surrounding a rotor, which is supported by bearings for rotation in the motor housing or compartment. In the case of ac motors, ac power applied to the motor creates magnetic excitation causing the rotor to rotate within the stator. The speed of this rotation is typically a function of the frequency of the applied ac input power (i.e., frequency) and of the motor design (i.e., the number of poles defined by the stator windings). A rotor shaft extending through the motor housing takes advantage of this produced rotation and translates the rotor's movement into a driving force for a given piece of machinery. That is, rotation of the shaft drives the machine to which it is coupled. The driving force is typically expressed as a horsepower (HP) or kilowatt (kW) rating, and is a function of the active material employed in the motor design.
Traditionally, the construction of large commercial ac motors is a labor-intensive, manual process. More specifically, the formation, insertion, and arrangement of coil windings with respect to the stator may be an arduous process. Typically, coil windings are formed by feeding conductive wire onto or about a rotating winding form, which loops the wire around wire guides or channels that are arranged in a sequentially arranged stepped configuration, thereby forming graduated bundles of coiled wire arranged in a generally parallel manner with respect to one another. However, in traditional coil windings, the conductor bundles are wound in a generally horizontal configuration. That is, the cross sectional width of each bundle of coiled wire, as determined with respect to the base of the wire guide or channel in which it is wound, is greater than its height. By contrast, the stator slots into which the bundles of coiled wire are inserted typically present a cross sectional profile with a vertical orientation, that is a cross sectional profile with a greater height than width. Accordingly, typical coil winding fabrication techniques require rearrangement of the bundles of coiled wire into a vertical configuration to more closely match the profile (i.e., vertical orientation) of the stator slots. Thus, once the bundles of coiled wire (i.e., conductor bundle) are removed from the winding form, an additional step to reconfigure the bundles into the vertical configuration is generally undertaken.
To reconfigure the bundles for insertion into a stator, a separate transfer tool is typically employed. Traditional transfer tools comprise vertical sorting members that receive and funnel the bundles of coiled wire into vertically oriented channels, thereby reconfiguring the bundles from the horizontal configuration to the vertical configuration. Once reconfigured into the vertical configuration, the bundles of coiled wire better correspond with the vertical orientation of the stator slots. Accordingly, the transfer tool may be coupled to an insertion tool and dragged through the interior of the stator core, thereby threading and feeding the bundles of coiled wire into the appropriate stator slots. However, by reconfiguring the bundles, the tightly packed organization of each bundle establish during the traditional coil winding is generally lost, thereby leading to current imbalance in the motor, which leads to reduced motor performance during operation.
Moreover, traditional fabrication techniques do not maintain the stepped configuration developed during the coil winding process. In other words, although conventional transfer tools may maintain segregation between the graduated bundles, the graduated or concentric stepped arrangement between the bundles is lost during the coil transfer and insertion steps. The stepped configuration is useful, however, in allowing coils at ends of the stator to be pressed into an axially nested arrangement (i.e., at the same general radial dimension) to reduce the space required for the winding ends. Thus, to achieve proper operational balance of the motor and to properly nest the bundles of coiled wire for formation of the coil winding end turns, the stepped configuration is generally reestablished after the bundles of coiled wire have been inserted into the appropriate slots of the stator. This phase of fabrication (i.e., reestablishment of the stepped configuration of the bundles of coiled wire) is typically completed manually, that is by hand. Manual arrangement of the bundles of coiled wire is a labor intensive and time-consuming process. Moreover the manual process, because of human error and imprecision, may lead to inconsistencies in the alignment of with the windings of each group and between the windings of each group, thereby leading to current imbalance and reduced motor performance during operation.
There is a need, therefore, for an improved technique for fabricating electric motors. More particularly, there is a need for a technique that improves the fabrication and installation of coil windings into a motor stator.